AN ALTERNATIVE INSERT OF 3 AMINO-ACIDS IS INCORPORATED INTO COLLAGEN XIV IN A DEVELOPMENTALLY-REGULATED FASHION

We have identified a novel splice variant of chicken collagen XIV whic h contains an insert of three amino acids (Val-Arg-Thr) in the sixth f ibronectin type III-like (FNIII) domain, The codons for these amino ac ids are inserted into the mRNA by skipping of a splice donor site and usage of another donor site 9 bp further downstream in the collagen XI V gene, The percentage of the new splice variant in the total collagen XIV mRNA varies between 22 and 46% in different embryonic tissues. Af ter hatching, however, this percentage increases dramatically and reac hes 86% in adult skeletal muscle and 58% in adult gizzard, indicating developmental regulation of this splicing event, Computer modeling sug gests that the three extra amino acids cause an increase in the size o f a flexible loop connecting two beta-strands in the sixth FNIII domai n, This increase might affect the exact arrangement of the FNIII domai n in the collagen XIV molecule, thereby modulating its interactions wi th other matrix molecules, (C) 1998 Federation of European Biochemical Societies.